The spectrum of $Li^{2+}$ is similar to that of:

Calculate the radius of the first orbit of $He^{+}$. (in $pm$)

Henry Moseley studied the characteristic $X$-ray spectra of elements. The graph which represents his observation correctly is: (Given $\nu =$ frequency of $X$-ray emitted; $Z =$ atomic number)

If $\lambda_0$ and $\lambda$ are the threshold wavelength and the wavelength of incident light,respectively,the velocity of the photoelectron ejected from the metal surface is:

Based on equation $E = -2.178 \times 10^{-18} \ J \ \frac{Z^2}{n^2}$,certain conclusions are written. Which of them is not correct?

Typical electronic energy gaps in molecules are about $1.0 \ eV$. In terms of temperature,the gap is closest to